Air cooling system for below freezing temperatures



June 30, 1964 A. R. DAVIDSON ETAL BELOW FREEZING TEMPERATURES 8Sheets-Sheet l Wan so? J1. JUL

INVENTORS Robert K. McCormock 8 y Arthur R. Davidson ATTORNEYS June 30,1964 A. R. DAVIDSON ETAL- 3,133,939

AIR COOLING SYSTEM FOR BELOW FREEZI Filed March 5, 1962 NG TEMPERATURES8 Sheets-Sheet 2 t f 36 36 k g, A 5 H 3+ r- TI 3 BY FIG.3.

+ I INVENTORS 5 '1 Robert K.McCor mock 8 E m Arthur R. Duvldson n 1964A. R. DAVIDSON ETAL 3,138,939

AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Filed March 5, 1962 8Sheets-Sheet 3 F lG.4.

IN VENTORS Robert K. McCormock 8 Fl G 5 Arthur R. Davidson ATTORNEYSJ1me 1964 A. R. DAVIDSON ETAL 3,138,939

AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Filed March 5, 1962 sSheets-Sheet 4 I I I I38 l2 M 32 I38 I I. I F '56 I I66 0 74 :.-d W

ll 5Q r 4o 64- o Z Z [O0 I I 54'' 12 I 5% 8+ Q I I /66 I I i \k FIG.6.

INVENTORS Robert K. McCormock 8 Arthur R. Davidson ATTORNEYS m 1964 A.R. DAVIDSON ETAL 3,138,939

AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Filed March 5, 1962 8Sheets-Sheet 5 FIG INVENTORS Robert K.McCormack a Arthur R. DavidsonTTORNEYS June 30, 1964 A. R. DAVIDSON ETAL 3,133,939

AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Filed March 5, 1962 8Sheets-Sheet 6 FIG.8.

INVENTORS Robert K. Mccormucka Arthur R. Davidson ATTORNEYS June 1964 A.R. DAVIDSON ETAL 3,

AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Filed March 5, 1962 8Sheets-Sheet 7 w. I L/ 1 I38", nu! 10 K I l g I24 I00 I 62- t I I 000 72INVENTORS Robert K. McCormcck & Arthur R. Davidson W KW ATTORNEYS June30, 1964 A. R. DAVIDSON ETAL 3,138,939

AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Filed March 5, 1962 8Sheets-Sheet 8 EVAPORATOR EVAPORATOR SER SURGE RECEIVE R INTERCOOLER 78SUCTION TRAP nos ORIFIGE TWO STAGE COMPRESSOR INVENTORS RobertK.McCormuck& FIG. IO. Arthur R. Davidson ATTORNEYS United States Patent7 3,138,939 AIR COOLING SYSTEM FOR BELOW FREEZING TEMPERATURES Arthur R.Davidson, American Falls, Idaho, and Robert K. McCormack, Lake Oswego,Oreg., assignors to Lamb-Weston, Inc., a corporation of Oregon FiledMar. 5, 1962, Ser. No. 177,525 7 Claims. (Cl; 62-155) Our presentinvention comprises means for maintaining the interior of a large,single space, insulated structure at below freezing temperatures, suchas a food storage warehouse maintained at minus F. The present inventioncomprises the use of a plurality of self-contained air cooling unitstotally enclosed within the refrigerated space, with no connections tothe exterior of the structure other than power supply lines and waterlines. The air cooling units preferably comprise two-stage hermeticallysealed compressors adapted to use Freon-22 or other suitablerefrigerants as the refrigerating medium. Hence basically the inventionis directed to a novel assembly wherein selfcontained, preassembled,automatic and interchangeable refrigeration systems are utilized inmultiples to produce a total refrigerating effect required for a singlecontrolled climate space. Such function is obtained by the use ofcompressor-condenser packages which are so interiorly heated, orsufficiently insulated, or both, to permit their operation inrefrigerated spaces maintained at even very low temperatures.

Thus, a principal object of the present invention is to provide a systemof the foregoing character comprising a plurality of individual aircooling units each comprising a refrigeration system including awater-cooled condenser, the Water-cooled condensers of all of said unitsbeing connected in parallel to common water supply and water returnlines whereby a constant flow of water is maintained in said commonlines so as to minimize the amount of insulation or heating required toprevent freezing of the common lines.

An additional object of the invention is to provide an inexpensive lowtemperature freezing system capable of being maintained at low cost,there being no necessity for operators, there being no central engineroom, and the system being entirely automatic in its operation. In thisrespect, although the system is ideally suited for low temperaturemaintenance of the order indicated (-5 F.) any temperatures belowambient temperature, as from Well below freezing to moderatetemperatures (as, e.g. 40 F.) may be maintained at a predeterminedconstant through use of the instant invention.

A further objective of theinvention is to provide large tonnagecapacities in refrigeration systems by the use of a plurality ofself-contained air cooling units which permit precharging ofrefrigerant, thus eliminating the necessity of expensive installationand maintenance of lengthy refrigeration systems extending from acentral engine room to zone cooling units.

Another objective of the invention is the provision of means foroperating compressor-condenser systems within the confines of a givenrefrigerated space with the components thereof arranged in such manneras to prevent freeze up or damage during operation or shutdown of thesystem.

A furtherobject of the invention is to provide a system of the foregoingcharacter eliminating the fabrication and installation of air supply andreturn ducts.

An additional object of the invention is to provide large tonnage aircooling systems in a manner permitting factory assembly of allcomponents except water and electrical components, thereby materiallyreducing the cost of installation and maintenance and assuringtrouble-free performance of the system.

3,138,939 Patented June 30., 1964 Another object of the invention is toprovide means of the character outlined in the foregoing by whichdefrosting is accomplished while maintaining the space temperature atthe desired level.

A further objective of the invention is to provide means of theforegoing character in which defrosting is automatically and effectivelycontrolled.

Another object of the invention is to provide air cooling units for usein such a system in which defrosting is preferably accomplished by theuse of hot gas in the refrigerating system, although other defrostingmethods are also applicable, such as water defrosting, electricdefrosting, etc.

An additional object of the invention is to provide means of theforegoing character in which a plurality of separate air cooling unitsare employed, permitting a unit failure to be corrected without losingstored materials due to spoilage as a result of mechanical failures.

These and other objects and advantages of the invention may be morereadily understood by reference to the following specification taken inconnection with the accompanying drawings, wherein like numerals referto like parts throughout, and in which a preferred embodiment of theinvention is illustrated and described.

In the drawings,

FIGURE 1 is a schematic plan view of a portion of the interior of alarge building incorporating the inventron;

FIGURE 2 is a partial cross-section through a building such asillustrated in FIGURE 1, the view being on an enlarged scale and takensubstantially from line 22 of FIGURE 1;

FIGURE 3 is a plan view of an individual unit taken substantially fromthe line 33 of FIGURE 2;

FIGURE 4 is a side elevation taken substantially from the line 44 ofFIGURE 3;

FIGURE 5 is an opposite side elevation taken substantially from the line55 of FIGURE 3;

FIGURE 6 is a horizontal section, on an enlarged scale, through one ofthe refrigerating units taken substantially along line 66 of FIGURE 8;

FIGURE 7 is a plan view of one of the air cooling units takensubstantially along line 77 of FIGURE 8;

FIGURE 8 is a vertical section through one of the air cooling unitstaken substantially along line 88 of FIG- 7 URE 6;

FIGURE 9 is a vertical section through one of the air cooling unitstaken substantially along line 9--9 of FIG- URE 6; and

FIGURE 10 is a schematic disclosure of the refrigerating system of anindividual unit.

The present invention is illustrated in association with alow-temperature storage structure 1ft preferably comprising a largerectangular, single space, insulated structure including a side wall 12,an opposite side wall 14, an end Wall 16 and an opposite end wall (notshown) One or more of the walls may be provided with access doors 18 andone or more of the walls may be associated with insulated vestibules 20for permitting the entry and exit of loaded vehicles. The structurenecessarily includes a floor 22 on which there are no substantialobstructions other than stored products. An insulated roof 24 issupported entirely by transverse trusses 26 extending from side to sideof the structure so that only an upper part of the interior spacecontains building elements, whereby vehicles may freely traverse theentire interior of the building and piles of material may be placed inany position on the floor and extend up to the lower edges of thetrusses. It is to be appreciated that the present invention may beincorporated in structures having different outlines and in which theremay be inter- J ior columns, the requisite of the structure being thatit encloses a large interior space.

The interior space is cooled in accordance with the present invention bya plurality of self-contained air cooling units 30, each individuallymounted closely beneath the roof 24, preferably midway between adjacenttrusses 26 and with their lower portions above the lower beams of thetrusses. In this respect it is to be noted that although the coolingunits herein specifically described involve the use of water cooledcondensers, evaporative or air cooled condensers are equally suitablefor use in the inventive combination. At any rate, such cooling unitsare preferably suspended, such as by means of rods 32 suitably fastenedat their lower ends, to angle bars 34 forming the corner edges of theframes of the units, the upper ends of the rods extending throughlongitudinal beams 36 extending between the trusses adjacent the roof24. The units are preferably arranged in a single row extending acrossthe building from one wall to the other along or closely adjacent amedian line of the building. Depending upon the load imposed upon theunits and their capacity, there may be a unit in each space between eachadjacent pair of trusses, or there may be a gap here and there, providedthat sufficient refrigeration capacity is present to take care of theload in the event that one, or possibly two, of the units should betemporarily shut down due to mechanical failure.

Access to the units is provided by means of a catwalk 38 extendingalongside the entire row of units, at a level such that access doors 40of the units may be opened to permit entry ito each unit, the accessdoors preferably facing the catwalk. Adjacent each unit there ispreferably provided a short ladder 42 leading to an elevated catwalk 44partially surrounding the unit whereby access to the upper portion ofthe unit may be had. A stairway 46 leads from the roof of the centralvestibule to the catwalk 38 and a ladder 47 leads from there to thefloor.

Suspended beneath the catwalk 38 there is provided a common condenserwater supply pipe 50, a common condenser water return pipe 52 and acommon condensate drain pipe 54, all of which are appropriatelyinsulated and run the length of the catwalk. A common electric wireconduit 56 is suspended adjacent the roof and runs alongside the row ofunits. The water supply and return pipes, the condensate pipe and thewiring in the electrical conduit are the only connections of the systemwhich run outside of the building, through the wall 16.

Each air cooling unit comprises an insulated compartment having oppositeside walls 60 and 62, a rear wall 64, a front wall 66 in which the dooris located, a bottom wall 68 and a top wall 70, all of which containsufiicient insulation to maintain the temperature within the compartmentat a comfortable working temperature above freezing. In this respect itis to be understood that the invention contemplates any means of heatingthe compressor-condenser package contained within the describedcompartment, as by insulation thereof, or any other means of heatingthese components such as to permit operation thereof directly within theconfines of the refrigerated space.

In any event, each air cooling unit comprises a low temperaturerefrigeration system including a compressor portion 72, a condenserportion 74 and an evaporator portion 76 connected together inrefrigerant flow relationship, with the compressor portion and thecondenser portion within the insulated compartment and the evaporatorportion located outside of and preferably on top of comprises ahermetically sealed, suction gas cooled, twothe compartment. Thecompressor portion preferably stage compressor 78 mounted on the floorof the compartment. Although the invention is not necessarily confinedto this type of compressor, it is stated as preferable as representing atype which prevents transfer of motor efiiciency heat loss from themotor to the confined space housing this compressor-motor combination.Similarly, although a two-stage compression system is indicated aspreferred, single-stage units may be desired under certaincircumstances.

The condenser portion preferably comprises an intercooler 80, a surgereceiver 82, a suction trap 84, and a water cooled condenser 86, all ofwhich are mounted upon or near the compressor. Although a singleevaporator may be utilized under certain circumstances, the evaporatorportion 76 preferably comprises a pair of evaporators 88 and 90connected in parallel in the system, one being mounted above the frontof the compartment and the other being mounted above the rear of thecompartment, with a space therebetween. Each evaporator is enclosedwithin a sheet metal wrap 92 which is open toward the center of the unitand which mounts a pair of air impelling units Q4 adapted to draw airthrough the evaporator from the space above the unit and the centralspace between the coils and impel the cooled air leaving the evaporatorshorizontally through the upper part of the building space in oppositedirections, one stream being directed toward the side wall. 12 and theother stream toward the side wall 14, as indicated in the arrows inFIGURE 1. Preferably the space between the evaporators is provided withside walls as indicated at 95, so that air is drawn into the evaporatorsfrom the uppermost part of the refrigerated space. The cold air which isopenly projected toward the side walls of the space comingles with theair within the space, the resulting colder portions thereof fallingtoward the floor and the warmer portions thereof rising toward theceiling to be recirculated through the evaporators. Other obvious fan orblower arrangements may be used: the air impellers may be arranged fordischarge in one direction only, or attached to appropriate ductwork, orpositioned for air travel vertically up or down, etc. At any rate, eachevaporator preferably sits in a condensate pan 97 from which acondensate drain line 98 extends downward into the interior of thecompartment and then laterally through the wall of the compartment tojoin the common condensate pipe 54. However, other means of collectingdefrost condensate may be desirable: condensate containers may bearranged within the refrigerated space for periodic removal, thecondensate becoming frozen and recovered as ice or snow. Condensate mayalso either be pumped back into the condenser water mains orre-evaporated back into the refrigerated space by either a source ofheat or a humidifying nozzle.

As herein depicted the referred to air cooling units are shown aspreferably extending along the upper center line of the refrigeratedspace. However, such multiple units can be optionally positioned alongthe end or side walls of the building. Alternatively, the units may bearranged in rows running the short dimension of the building, therebeing a sufficient number of units in any event to meet the requiredcooling load. The system also lends itself to arrangements wherein thecooling units may be mounted upon appropriate conveyances whereby theyare rendered completely portable in such instance having appropriatetemporary water and power connections. Or on the other hand, theindividual cooling units may be mounted in doorway or appropriate wallopenings, in which cases air from an air cooled condenser is easilydischarged to the outside, while refrigerated air is discharged to theinterior of the structure, where separate, individual units are so used,factory assembly and prepackaging thereof for immediate use withoutcumbersome installation procedures renders the use of same mostadvantageous.

The refrigerating system is schematically indicated in FIGURE 10, inwhich the directional signs on the pipes indicate refrigerant flowduring normal flow of cooling refrigerant to the two evaporators 88 and90 and return to the compressor 78, and the directional arrows besidethe pipes indicate refrigerant flow during the time that the evaporator90 is being defrosted. It is to be appreciated that the refrigerant flowduring the time that the other evaporator 88 is being defrosted wouldcorrespond.

The expanded refrigerant gas enters the compressor 78 through a suctionline 100 connected to the low pressure cylinders or first stage part 102of the compressor. The hot gas under the first stage of compressionpasses through passageways schematically indicated at 104 into the highpressure cylinders or second stage part 106 of the compressor. Thehighly compressed gas is then conducted by discharge line 108 into thetop of the shell of the water cooled condenser 86 through aspring-loaded check valve 110. The liquefied refrigerant is then drawnthrough pipe 112 into the internal coils of the heat intercooler 80. Alarge branch of the pipe 112, indicated at 114, leads to the bottom ofthe surge receiver 82. A small branch 116 of the pipe 112 leads to theshell of the intercooler through a solenoid valve 118 and an expansionvalve 120 controlled by a thermal bulb 122 mounted on the pipe 104,whereby a portion of the liquid refrigerant is drawn off and expanded inthe shell of the intercooler 80 to subcool the liquid in the pipe 112.The expanded gas is drawn back from the intercooler into the passage 104through a connecting pipe 124. The solenoid valve 118 is constantly openwhen the compressor is in operation.

The subcooled liquid is discharged from the intercooler through pipe 126into a header having a branch 128 leading to evaporator 90 and a branch130 leading to evaporator 88. The flow through pipe 128 is controlled bya normally open solenoid valve 132 and an expansion valve 134 having asensing bulb 136 on a branch return line 138. The flow through branch130 is controlled by a normally open solenoid valve 139 and an expansionvalve 140 having a sensing bulb 142 on a branch return line 144. Thebranch return lines 138 and 144 join a return line 146 which enters thesuction trap 84. Gas from the suction trap 84 is drawn off through thesuction pipe 100. Liquid from the suction trap 84 passes through a pipe150 controlled by a solenoid valve 152 and having a fixed orifice 154therein. The solenoid valve 152 is open whenever the compressor isrunning.

Hot condensed gas may be drawn from the discharge line 108 through apipe 156 having a branch 160 leading into the evaporator 90 and throughthe tubes therein which ordinarily carry expanding refrigerant, and abranch 162 leading to the evaporator 88 and through the tubes thereinwhich ordinarily carry expanding refrigerant. Pipe 160 is normallyblocked by a solenoid valve 164 and pipe 162 is normally blocked by asolenoid valve 166. Another pair of normally open solenoid valves 168and 170, are adapted to shut branch suction pipes 138 and 144respectively. Solenoid valves 132, 164 and 168 act in unison so thatwhen defrost gas is desired in evaporator 90, solenoid valve 132 isclosed, solenoid valve 164 is opened, and solenoid valve 168 is closed.Likewise, solenoid valves 139, 166 and 170 act in unison so that whendefrost gas is desired in evaporator 88, solenoid valve 139 is closed,solenoid valve 166 is opened, and solenoid valve 170 is closed. In theillustrations of the defrost cycle by means of the arrows set at thesides of the pipes, defrosting gas is flowing through evaporator 90andrefrigerating liquid is flowing into and expanding in evaporator 88.

Under the foregoing circumstances the evaporator 90 is acting as apartial condenser, and hot liquid and gas are flowing through pipe 138into a pipe 172 which joins a header 174 through a spring loaded checkvalve 176. The header 174 discharge liquid refrigerant into the surgereceiver 82 through a connection 178, and gaseous refrigerant into thecondenser 86 through a connection 180. While this is going on,refrigerating liquid is still 'flowing into evaporator 88, from whichexpanded gas is possible within the purview of the invention.

being returned to the compressor. Similarly, when defrosting gas isflowing through evaporator 88 refrigerat ing liquid is flowing in thenormal fashion into evaporator 90. In this instance refrigerant isreturned from evaporator 88 through a pipe 173 and spring loaded checkvalve 177 into header 174. Through the interconnections provided thereis always a supply of sufiicient gas to the compressor to feed liquidrefrigerant to one or the other, or both, of the evaporators, and whenrequired, simultaneously to feed hot compressed refrigerant to one ofthe evaporators for defrosting purposes and liquefied refrigerant to theother for cooling purposes.

Mounted within the zone of cooling influence of each air cooling unitthere is a temperature sensing means such as a thermostat 184 preferablylocated within the stream of air entering the space between theevaporators 88 and 90, so as to sense the temperature of the airinfluenced by the particular unit as a whole and to control the on-oifcycling of that unit accordingly. The thermostat 184 is electricallyconnected to the motor of compresor 78 and the solenoid valves 118 and152 so that whenever the compressor operates the valves 118 and 152 areopen, and whenever the compressor stops the two valves are closed.

Electric clock timing means 186 is provided in association with eachunit so that evaporator 88 is periodically defrosted for a short periodof time while evaporator continues to act as an air cooler. Preferablythere is one timing means 186 controlling all units sequentially so thatno more than one or possibly two of the entire series of evaporators isbeing defrosted at any one time, although it is to be understood thatother methods of automatically preparing the defrost cycle, and withoutthe use of time clocks and solenoid valves, may be utilized. Thearrangements of pipes and check valves, and the solenoid valves 132,139, 164, 166, 168 and constitute defrosting means to shut off the flowof liquefied refrigerant to either of the evaporators 88 and 90 fordefrosting purposes while the flow of liquefied refrigerant to the otherof said evaporators continues. Each defrosting action is so timed as tocompletely clear the particular coil of frost once every certain numberof hours.

In the event of mechanical failure of any one unit, the remainder of theunits will carry the load until repairs, or replacement of an entireunit, may be effected.

Associated with each air cooling unit are branch water pipes, a branchwater supply pipe 190 leading water from the common supply pipe 50 tothe water cooled condenser 86 and a branch water return pipe 192returning the water to the common return pipe 52. -Valve and bypassmeans comprising a three-way, modulating, pressure actuated water valve194 and a bypass pipe 196 keep the flow of water in pipes 190 and 192constant. As the presure in the condenser rises, the amount of waterbypassed through pipe 196 falls and the amount of water permitted toenter the condenser rises, and vice versa. Therefore, the supply throughthe common pipes is constant at all times, protecting the water supplyand return system from freezing.

While we have herein shown and described the defrosting cycle as beingaccomplished by hot refrigerant, it is to be appreciated that thepresent invention may utilize or be supplemented by any other means ofdefrosting, such as electrical heating coils, water defrosting and thelike. Also, while we have herein shown and described a hermeticallysealed two-stage compressor, it is to be appreciated that the inventioncontemplates the use of any other type of compressor capable of producing low temperatures in the cooling surfaces.

It should be apparent to those skilled in the art that many othermodifications in arrangement and detail are For example: where aircooled, each air cooling unit is so arranged as to permit only theevaporator portion thereof to project below the roof line, with thecompressor-condenser portion extending above the evaporator and abovethe roof line. Such not only facilitates the use of air cooledcondensers, but also conserves space within the refrigerated structure.Obviously, the arrangement may be such that individual evaporators arearranged on either one side or the other of the compressor-condensercompartment, instead above or beneath the same, thus reducing theover-all height of such air cooling unit.

In addition the assembly is conducive to the use of cooling towers whichcan be utilized in conjunction with such air cooling units. In suchevent the condenser water lines are run vertically between the aircooling unit and the cooling tower thereabove, thus eliminating thenecessity of running water piping the length of the room. This alsopermits collection of defrost water condensate within the heatedcompressor-condenser enclosure, said condensate being pumped through thecondenser Water pump, also located in the heated enclosure, from whenceit passes through the condenser for return to the cooling tower. Thus,such defrost condensate water may be used as a source of make up waterto the cooling tower, providing the latter not only with cooler waterbut with distilled water as well.

From the foregoing explanation it will be understood that the basicconcept of this invention permits installation of all the completerefrigeration system components within the confines of the cold roomspace. The equipment can, in the described manner, be successfullyoperated under the conditions of temperature and/ or humidity found indifferent sizes and types of cold storage rooms. By first enclosing thecompression and condensin-g equipment within a heated compartment theassembly of the invention can function satisfactorily despite externallowered temperatures; further, by using hermetically sealed compressorsthe friction heat of the drive motors is transmitted to the refrigerantsuction gas, instead of to the surrounding space. The several advantagesof such a novel arrangement are manifest: by rendering these relativelysmall refrigeration systems automatic in operation, the operatingengineering staff is substantially reduced and additional facilitiessuch as engine rooms adjacent to the cold storage room, or long pipingruns to such engine rooms, are eliminated. Furthermore, existingfacilities can be expanded by the use of the instant assembly withoutthe necessity of enlargement of the then in place, already operatingrefrigeration system.

All such modifications as the foregoing, as well as others which comewithin the true spirit and scope of the following claims, are consideredto be a part of our invention.

We claim:

1. An air cooling system for maintaining the interior of a single space,insulated structure at below freezing temperatures, comprising aplurality of self-contained air cooling units mounted in the upper partof said space, each of said units comprising an insulated compartmentand having a low temperature refrigeration system including a compressorportion, a condenser portion and an evaporator portion connectedtogether in refrigerant flow relationship, expansion means, saidcompressor portion and said condenser portion being within saidcompartment and said evaporator portion being outside of saidcompartment, said condenser portion comprising a watercooled condenser,said evaporator portion comprising a pair of air cooling evaporatorsconnected in parallel in said refrigeration system, and saidrefrigeration system having defrosting means to shut off the flow ofliquefied refrigerant to either of said evaporators for defrostingpurposes while permitting the flow of liquefied refrigerant to the otherof said evaporators to continue, air propelling means arranged to causeair from said space to traverse said evaporators and to propel the airleaving said evaporators openly across the upper part of said space, atemperature sensing means responsive to the temperature of air enteringthe evaporator portion of said unit to control on-off cycling of saidunit thereof, a common water supply pipe and a common water return pipetraversing said space, a plurality of branch water supply and branchwater return pipes respectively connecting said Water cooled condensersin parallel to said common water supply and common water return pipes,means to maintain the interior of each of said insulated compartments atabove freezing temperatures, and timing means periodically actuatingsaid defrosting means of said unit sequentially.

2. The structure set forth in claim 1 wherein said defrosting means isprovided with means to direct hot compressed refrigerant from saidcompressor portion into an evaporator being defrosted, and means todirect liquefied refrigerant from said condenser portion into the otherof said evaporators While one of them is being defrosted.

3. A refrigeration means for maintaining an interior space at belowfreezing temperatures, comprising a plurality of insulated and heatedcompartments, a preassembled, automatic and interchangeablerefrigeration unit in each of said compartments, each of said unitshaving a low temperature refrigeration system including a compressorportion, a condenser portion and an evaporator portion connectedtogether in refrigerant flow relationship, expansion means, saidcompressor portion and said condenser portion being within saidcompartment and said evaporator portion being outside of saidcompartment, said condenser portion comprising a water cooled condenser,said evaporator portion comprising a pair of air cooling evaporatorsconnected in parallel in said refrigeration system, and saidrefrigeration system having defrosting means to shut off the flow ofliquefied refrigerant to either of said evaporators for defrostingpurposes while permitting the flow of liquefied refrigerant to the otherof said evaporators to continue, air propelling means arranged to causeair to traverse said evaporators and to propel the air openly therefrom,temperature sensing means responsive to the temperature of air enteringsaid evaporator portion to control on-oif cycling thereof, a Watersupply pipe and a water return pipe connected to said Water cooledcondenser, valve and bypass means including a three-way, modulating,pressure actuated valve connecting said water supply pipe to said waterreturn pipe for maintaining constant flow of water in said pipes, timingmeans periodically actuating said defrosting means, and means tomaintain the interior of each of said compartments at above freezingtemperatures.

4. The structure set forth in claim 7 wherein said defrosting meanscomprises means to direct hot compressed refrigerant from saidcompressor portion into an evaporator being defrosted, means to directliquefied refrigerant from said condenser portion into the other of saidevaporators while one of them is being defrosted, and means to receiveand temporarily store liquefied refrigerant leaving the evaporator beingdefrosted.

5. A refrigeration means for maintaining an interior refrigerated spaceat from below freezing temperatures to below about 40 F. comprising aplurality of removable and insulated compartments positioned in saidinterior space, means to maintain the interior of each of saidcompartments at substantially above freezing temperatures, apreassembled, automatic and interchangeable refrigeration unit in eachof said compartments, each of said units having a low temperaturerefrigeration system including a compressor portion and a condenserportion, coolant fluid supply and return means for said condenserportion, expansion means, an evaporator portion connected together inrefrigerant flow relationship with said compressor and condenserportions, said compressor portion and said condenser portion beingwithin said compartment and said evaporator portion being outside ofsaid compartment but within said interior refrigerated space, saidevaporator portion comprising a pair of evaporators connected inparallel in said refrigeration system,

said refrigeration system having defrosting means to shut 01f the flowof liquefied refrigerant to either of said evaporators for defrostingpurposes While permitting the flow of liquefied refrigerant to the otherof said evaporators to continue, and air propelling means arranged tocause air to traverse said evaporators and to propel the air openlytherefrom into said interior space.

6. A refrigeration means for maintaining an interior refrigeratedwarehouse space at temperatures from subzero F. to about 32 F.comprising a plurality of removable and insulated compartmentspositioned in said interior space, means to maintain the interior ofeach of said compartments at above freezing temperatures, asubstantially preassembled, automatic and interchangeable air-coolingunit in each of said compartments, each of said units having a lowtemperature refrigeration system including a compressor portion and acondenser portion, coolant fluid supply and return means for saidcondenser portion, expansion means, an evaporator portion connectedtogether in refrigerant flow relationship with said compressor andcondenser portions, said compressor portion and said condenser portionbeing within said compartment and said evaporator portion being outsideof said compartment but within said interior refrigerated warehousespace, said evaporator portion comprising an evaporator interconnectedwith said refrigeration system, said refrigeration system havingdefrosting means to periodically shut off the How of liquefiedrefrigerant to said evaporator for defrosting ptnposes, and airpropelling means arranged to cause air to traverse said evaporator andto propel the air therefrom into said interior refrigerated warehousespace.

7. A refrigeration means for maintaining an interior refrigeratedwarehouse space at temperatures from subzero F. to about 32 F.comprising a plurality of substantially preassembled air cooling unitslocated inside the refrigerated Warehouse space, each of said unitscomprising an insulated compartment portion and an uninsulated portion,said insulated compartment portion containing a refrigeration compressorand a refrigeration condenser, said uninsulated portion containing anevaporator and a fan positioned and adapted to move warehouse air tosaid evaporator, said evaporator, condenser and compressor beingconnected together in refrigerant flow relationship, heating means tomaintain said insulated compartment above about 32 F., defrosting meansto periodically defrost said evaporator, fluid coolant supply andexhaust means for cooling said condenser, drain means for disposing ofcondensate from said evaporator, control means comprising a thermostaticmeans responsive to air temperature to maintain said range of saidtemperatures, and means to automatically time said periodic defrost.

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6. A REFRIGERATION MEANS FOR MAINTAINING AN INTERIOR REFRIGERATEDWAREHOUSE SPACE AT TEMPERATURES FROM SUBZERO *F. TO ABOUT 32* F.COMPRISING A PLURALITY OF REMOVABLE AND INSULATED COMPARTMENTSPOSITIONED IN SAID INTERIOR SPACE, MEANS TO MAINTAIN THE INTERIOR OFEACH OF SAID COMPARTMENTS AT ABOVE FREEZING TEMPERATURES, ASUBSTANTIALLY PREASSEMBLED, AUTOMATIC AND INTERCHANGEABLE AIR-COOLINGUNIT IN EACH OF SAID COMPARTMENTS, EACH OF SAID UNITS HAVING A LOWTEMPERATURE REFRIGERATION SYSTEM INCLUDING A COMPRESSOR PORTION AND ACONDENSER PORTION, COOLANT FLUID SUPPLY AND RETURN MEANS FOR SAIDCONDENSER PORTION, EXPANSION MEANS, AN EVAPORATOR PORTION CONNECTEDTOGETHER IN REFRIGERANT FLOW RELATIONSHIP WITH SAID COMPRESSOR ANDCONDENSER PORTIONS, SAID COMPRESSOR PORTION AND SAID CONDENSER PORTIONBEING WITHIN SAID COMPARTMENT AND SAID EVAPORATOR PORTION BEING OUTSIDEOF SAID COMPARTMENT BUT WITHIN SAID INTERIOR REFRIGERATED WAREHOUSESPACE, SAID EVAPORATOR PORTION COMPRISING AN EVAPORATOR INTERCONNECTEDWITH SAID REFRIGERATION SYSTEM, SAID REFRIGERATION SYSTEM HAVINGDEFROSTING MEANS TO PERIODICALLY SHUT OFF THE FLOW OF LIQUEFIEDREFRIGERANT TO SAID EVAPORATOR FOR DEFROSTING PURPOSES, AND AIRPROPELLING MEANS ARRANGED TO CAUSE AIR TO TRAVERSE SAID EVAPORATOR ANDTO PROPEL THE AIR THEREFROM INTO SAID INTERIOR REFRIGERATED WAREHOUSESPACE.